1.) Recirculating Aquaculture Systems

Carlos MartinezRoy Yanong and Debbie Pouder

• Main goals• Circulation of water• Biofiltration (removal of ammonia, nitrite)• Solids capture (suspended, colloidal, dissolved)• Gas exchange (oxygen/carbon dioxide)• (Pathogen reduction)• Minor goals• Ion adjustment (nitrate, bicarbonate, foam, color)(Simplified strategies, Ron Malone, LSU)

• Tanks/vats: fish holding areas• Filtration:• Mechanical: solids/particulate removal (biological?)• Biological: ammonia/nitrite removal (mechanical?)• Chemical: removal/addition of dissolved compounds• Sterilization: pathogen reduction• Degasser: CO 2, H 2S• Aeration/oxygenation: O 2• Sump: reservoir for water treatment• Pump: circulation

TanksSolids Removal (~mechanical)Biofiltration (biological: TAN, NO 2)Degassing/Aeration (O 2, CO 2)Chemical FiltrationSterilization

• Solids removal• Uneaten food• Fish waste• Organics• Types• Floss/foam/sponge• Pleats• Sand• Rotating drum• Bead

• Rid water of your enemies!• Ammonia, nitrite• Autotrophs• Good, nitrying bacteria• Convert ammonia to nitrite, nitrite to nitrate• Need oxygen and alkalinity• Heterotrophs• “Bad” bactgeria Feed on organic mater, include opportunisticpathogens• Need oxygen and organic debris

• Thick film reactor• Anything you need to backwash• Heterotrophs overrun• Autotrophs starve• Thin film reactor• Autotrophs favored• Limited organic build-up for heterotrophs

THICK FILM REACTOR• Heterotrophs overrun• Sponge filter• Undergravel filter• Rapid sand filterTHIN FILM REACTOR• Autotrophs favored• Wet/dry filter• Fluidized sand filter• Rotating biologicalcontactor (RBC)

• Chemical change—add or remove chemicals• Alkalinity, hardness• Ammonia, chemical treatments, chlorine, chloramine• Active carbon• Zeolite (ammonia adsorbing clays)• Ion-exchange resins• Water softeners: remove divalent cations (Ca 2+ ,Mg 2+ , etc.)• Dealkalizers (remove anions)• Oyster shell / coral gravel

• Reduce (not eliminate!) unwanted pests• Two major types• Ultraviolet (UV)• Ozone• Only works on water that contacts it!• Not on surface bacteria• Not effective against shedding by fish in system toother fish• Not helpful if management poor• In-line vs. separate loop

• “Zap dose”—dose required to ‘kill’ organism• Intensity/wattage of lamp• Contact time/flow• Water clarity• Size of organism/biological facgtor• Size 40 – 60% above target zap dose• Maintenance important!• In general• Gram negative < Gram positive < viruses < sporeformingbacteria < protozoan parasites• Also dependent upon life stage of organism

• Highly reactive molecule that will oxidize manyorganic and inorganic molecules• Does not oxidize ammonia appreciably• Does oxidize nitrite• Can improve efficiency of biofiltration• Fewer organics (food for heterotrophs)• Decrease nitrite• Potential nitrite spikes if ozonation stops• Need contact chamber• Personnel safety• Big facilities

• Remove unwanted dissolved gasses• Carbon dioxide, nitrogen, hydrogen sulfide• Add oxygen

• Aeration• Add oxygen to water via air• Blower, airstones• Oxygenation• Add pure oxygen• Intensive systems• $$